The movie’s structure is fragmented, as it alternates between three distinguishable plot threads.
A man jogging through suburban London grabs his heart, and collapses. He wakes up in a hospital bed. The nurse tending him gives him water. She leaves. He pulls down the bed covers to discover that his lower right leg has been amputated. He screams.
Elsewhere, intelligence operative Konratz (Marshall Jones) returns to his home country, an unidentified Eastern European totalitarian state. Upon being debriefed by a superior officer, Konratz steps around the table and places a hand on the other man’s shoulder, paralyzing and thereby killing him.
Back in London, MPS Detective Superintendent Bellaver (Alfred Marks) investigates the deaths of several young women in the city. The women, picked up at nightclubs by Keith (Michael Gothard), have apparently been killed by the same individual, and some of the bodies have been drained of blood.
The centerpiece of the movie is a nearly fifteen minutes long police – murder suspect car-chase/foot-chase sequence through suburban London.
Vincent Price plays Dr. Browning, whose clinic specializes in limb and organ transplantation.
Christopher Lee plays Fremont, the head of Britain’s (unnamed) intelligence services.
Peter Cushing plays Major Benedek, an official in the Eastern European country; a very brief cameo role.
The three plotlines converge in a chilling and unexpected climax.